Visible solar-ray supply system for space station

Acta Astronautica Vol. 13, No. 2, pp. 71-79, 1986

0094-5765/86 $3.00+ .00 © 1986 Pergamon Press Ltd.

Printed in Great Britain.

VISIBLE SOLAR-RAY SUPPLY SYSTEM FOR SPACE STATIONt KEI MORI Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223, Japan and NOBUHIKO TANATSUGUand MASAMICHIYAMASH1TA Institute of Space and Astronautical Science, Tokyo 153, Japan

(Received 26March 1985) solar-ray supply system presented here will mainly provide the visible solar ray necessary for the various activities in the space station, such as cultivation experiments on plants, fishes, birds and animals, room lighting for modules, and crew sun-bathing. Even natural solar rays reaching earth surface contain harmful rays for human beings, animals, higher plants and algae: Ultraviolet rays of medium (UV-B) and long wavelength (UV-A), infrared and heat rays, are all harmful to life. On a space station, the most dangerous short-wavelength ultraviolet (UB-C), X-ray and gamma-ray are additionally included, besides those cited above in markedly higher intensity. The range of rays useful and harmless to life is the visible band of wavelengths. No conclusive studies have been conducted concerning the unexpected powerful effects on the growth of plants and algae that can be brought by pure visible solar rays, in comparison with the corresponding effects of other kinds of artificial light source. Abstract--The

1. CONCEPT OF

Light intensity controllers are provided on the couplers equipping the individual branches. During the periods of no sunlight, artificial light from electric light source such as Xenon lamp is fed into the trunk for distribution through ducting common with that for the solar rays. At the terminal points of utilization, light dispensers of design suitable for each function are installed. Assuming an overall system efficiency of 50%, a luminous flux of 500 000 lm will be ensured by a 3.17 m diameter solar-ray collector feeding a 3 cm diameter trunk. The present paper is focused on the aspects of the present system associated with the study of life science, but the system is also available for other applications requiring a wider spectrum range, such as laser installations excited by solar rays, photochemical plants[4-6] and facilities utilizing the infrared range of solar rays as heat source.

SOLAR-RAY SUPPLY SYSTEM

This paper describes the further results obtained in connection with the Phase-A Level Study 2. The Phase-A Level Study was one of the seven International Study Tasks (IST) for the NASA Space Station Project Proposed by Japan. The Study was conducted in conformity with the approach[2]. The concept of the solar-ray supply system is shown in Fig. 113]. The solar rays are collected and concentrated by a factor of 10 000, by means of a solar-ray collector assembly composed of many small Fresnel lenses. The solar-ray collector is installed at an appropriate position outside the space station module, and is made to track the sun. Limitation of the admitted spectral band to the visible part of solar rays (350-850 nm of wavelength) is accomplished by utilizing the chromatic aberration of single Frensnel lens. The solar rays focused by each small lens are fed through the well-polished terminal end of a flexible light-conducting fiber, to be confined within its quartz core for transmission to the required location. The flexible fibers from the array of Fresnel lens converge and connect with the rigid large-diameter trunk, which channels the collected solar ray into space station module, Upon entering the module, the solar rays are further transmitted through rigid trunk installed in the module for distribution to the various points of utilization via branch lines fed from the trunk.

2. REQUIREMENTS FOR THE LIGHT TO BE

SUPPLIED

2. I Quantity of Light Table 1 shows the quantities of solar-ray and artificial light required for each application.

SOLAR-RAYS INCIDENT ON SPACE STATIONS

3. CHARACTERISTICS OF

3.1 Solar constant value In this study, the following values given in reference documents have been used:

t Paper presented at the 35th Congress of the International Astronautical Federation, Lausanne, Switzerland, 8-13 October 1984.

solar constant value = 1353 W/m 2 or 1,940 cal/cm2/min radiation error = +-21 W/m 2 or +-0.03 cal/cm2/min. 71

K. MORIet al.

72 Sun Tracking System Mechon sm

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Fig. 2. Solar spectral irradiance. 4. CONCEPT OF SOLAR-RAYCOLLECTOR SYSTEM

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4. ! Prerequisite The solar-ray supply system should be considered as a versatile concept adaptable to the changes that will be expected in the requirements with progress of the space station project.

Fig. 1. Concept of solar-ray supply system. 3,2 Spectral radiant intensity of solar-rays The sun radiates energy across a broad spectrum ranging from X-rays to radio waves (Fig. 2). The peak of the spectrum is located at 480 nm, and about 77% of the radiant energy lies in the 300-1200 nm range. About 1% lies below 300 nm and about 22% above 1200 nm. 3.3 llluminance of solar-ray on space station The illuminance of solar-rays on a space station can be calculated by the following formula:

Ev = Km f:eV(h)dh where Ev is illuminance (Ix) and d@e/dh is spectral radiant flux of the solar-ray per unit area at wavelength h. Km is 680 +-- 41 m/W, when the above formula is applied to the primary standard with maximum relative luminous efficiency. V(h) is standard relative luminous efficiency. The above equation yields the value of 126 760 Ix. As a result, the solar-ray collector will require an effective area and corresponding diameter as shown in Fig. 3, where the efficiency of the entire system is adopted as parameter.

4.2 Solar-ray supply system 4.2. l System configuration: The configuration of the solar-ray supply system reviewed in this study is shown in Fig. 1. 5. KEY HARDWARE

5.1 Solar-ray collector 5.1.1 Separating the visible spectrum: In this study, two method of separating the desired spectrum were considered. 5.1.2 Comparison of solar-ray collectors: (1) Mirror System. When a Cassegrain mirror is used, the apparent focal length can be shortened. However, as the first reflecting mirror condenses energy of relatively low density, the focal point can be shifted unless the mirror is finished to high accuracy. A similar result will occur also in the event of deformation due to a temperature change. In the case of the second reflecting mirror, very high energy tends to gather, which may damage the mirror due to the very marked temperature differences that will be occasioned by shifting of the focal point.

<

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Table 1. Luminous requirement Daytime

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3

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: 3 ,~ 41

Cultivate Experiment Higher Plant Algae Illumination/room Sunbathing

205,000 10,600 75,000 72,000

20,500 lumen 10,600 75,000 0

Total

363,000

106,000 lumen

°o

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Luminance Flux

4 ,m,

Fig. 3. Area and diameter of solar-ray collector.

Visible solar-ray supply system Table 2. Comparisonof solar-my collectorsystems Lens System Medium Lens System

Small Lens System

Type

Fresnel

Fresnel

Focal length F no

600 mm 2.0

40 - 125 mm 1.0 ~ 1.15

Fiber diameter NA

Bundle,approx, l0 mm¢ 0.2

Single core, approx. 0.5-1.8 mm~ 0.4

Thickness

Approx. 800 mm

Approx. 120-350 mm

Weight

,6

O

Alignment

0

Optical System Material

Plastic

Plastic

Resistance to ultraviolet rays and cosmic rays

,6

A

Thermal condensation

A

0

Compatibility with fiber

A

O

In the millor system, there is generally no chromatic aberration, so that most of the solar radiant energy is condensed. This indicates the need for adopting a filter to separate the spectrum. (2) Medium-Sized Lens Unit System. In a mediumsized lens unit system, separation of the spectrum is easily obtained utilizing the chromatic aberration of Fresnel lens.

73

The difficulty will lie in coping with large changes of temperature. Another inconvenience will be the thick panels that will result upon assembly into units. (3) Small-Sized Lens System. A small-sized lens system will have lens units on the panel, incorporating a device to withstand the changes in temperature. It will also provide significant reduction in the weight of the panel. Also the small diameter of the lenses (about 40 mm) a single core flexible fiber for receiving the light at the focal point. This will contribute to enhancement of light receiving efficiency. The spectrum could also be separated by utilizing chromatic aberration, but, this will increase the number required of lenses and conducting fiber cables. A comparative evaluation of the above two systems is presented in Table 2. 5.2 Pointing system 5.2.1 Required pointing accuracy: The pointing accuracy required for proper functioning of the chromatic aberration spectrum cutoff system is 0.02. 5.2.2 Pointing system: One form of pointing system can be considered, depending upon the attitude control system of the space station and on the location of the solar-ray collector. The gimbal freedom and the tracking angle speed will differ accordingly, but the system configuration and method of control will be practically the same. The characteristics of the pointing system are given in Table 3. 5.2.3 Control system: The pointing control system consists of a tracking system that will seek to reduce to zero the tracking error signal of the solar sensor, and a rate damping system for stabilizing the attitude of the space station and the tracking system.

Table 3. Comparison of functions and performance of pointing systems System

Remarks

Space station attitude control system

Inertia control or ground reference control

Location of solar-ray collector

Installed on equi-solar direction side of solar-paddle

Basic system Gimbal Gimbal freedom tracking speed • Inner gimbal • Outer gimbal • Rotary gimbal

2-axis stable platform + Solar tracking equipment +-- a few degrees * - a few degrees **

Operation mode

• Tracking mode • Screw mode (Return mode) • Caging mode

Gimbal actuator (Torquer)

Brushless motor or step motor

* Gimbal freedom necessary for stabilizing paddle equi-solar direction error angle ** Slew mode (when return operation is available)

K. MORIet al.

74

5.3 Optical transmission path 5.3.1 Function: The optical transmission path serves

5.4 Optical tranmission couplers 5.4.1 Function: Various couplers are necessary for

to transmit the light collected and condensed by the solarray collector and to conduct this light to the points of utilization. 5.3.2 Types and features of optical transmission paths: Optical transmission paths are constituted of either (a) fixed or (b) flexible light-conducting cable. Each type presents advantages and inconveniences. 5.3.3 Comparison of materials used for optical transmission path: Pure quartz fiber, Ge-doped core fiber and quartz glass rod can be used on a space station. The different characteristics (NA, wavelength, radiation resistance and temperature resistance) of these materials are compared below.

transmitting the solar light condensed by the solar-ray collector to the different modules of the space station. 5,4.2 Types of couplers: The types of couplers required in a space station are as follows.

(1) NA (Index Representing Allowable Range of Angle of Incidence): Ge-doped core fiber . . . . . . . . . . . . . . . . 0.28 Pure quartz core fiber (1) PCF . . . . . . 0.4 Quartz glass rod . . . . . . . . . . . . . . . . . . . 0.4 (2) Wavelength Characteristics: The losses of Ge-doped'tJore fiber and pure quartz core fiber are roughly shown in Table 4, as function of wavelength. In the case of Ge-doped fiber, the loss in the visible wavelength region is greater than that of the pure quartz fiber, due to the adverse effects brought by the absorption band (363 rim) of germanium dioxide. (3) Radiation Resistance Characteristics: A study on the increase of Ge dope core fiber loss and the pure quartz core fiber loss, revealed that the latter fiber has more satisfactory radiation resistance characteristics. The dosage rate of solar rays in space is 5R per day. When a ten year period of use is considered, then the Ge dope fiber can be used. The increase of loss depends upon the radiation dosage rate. Little or no increase in the loss of the pure quartz core can be found in the case of a dosage rate of 5R/day. (4) Temperature Resistance Characteristics: The transmission performance of the fiber drops markedly below " - 2 0 C . " The results of the performance comparison of materials used for optical transmission paths is summarized in Table 4.

(1) Fixed Couplers: For rigidly connecting transmission ducting end to end. (2) Rotative Couplers: For ensuring the passage of light through interfaces involving rotative displacement of ducting, such as in the gimbal mechanisms of the solar-ray collector. 5.5 Light intensity controllers 5.5.1 Function: Light intensity controllers regulate the quantity of light distributed to each application. The first stage light intensity controller is installed upstream of the point of convergence with the supply from artificial source. Distributed light that finds no use at the end of the network will be reflected back toward the solar-ray collector, or else the supply from solar-ray collector reduced. 5.6 Light dispenser 5.6.1 Function: The light dispenser serves as terminal outlet for dispensing the transmitted light, to be used as source for lighting or sunbathing. 5.6.2 Types of light dispenser: (1) For Lighting: The dispenser radiates light similarly to a currently used tube type fluorescent lamp. (2) For Sunbathing: Light is radiated from the terminal outlet in a diverging flux, so that the intensity of radiation can be adjusted by the distance between dispenser and subject. 5.7 Artificial light source 5.7.1 Function: Artificial light is supplied electrically when the position of space station or other factors prevent the solar-ray collector from functioning. 5.7.2 Selection of artificial light source: The artificial light source (Fig. 4) must meet the following two requirements.

Table 4. Performance comparison of materials used for optical transmission path Ge Dope Core Fiber

Pure Quartz Fiber PCF (Polymer Clad)

NA

C)

~

Wavelength Characteristics

A

0

0

Radiation Resistance Characteristics

A

0

C)

Mechanical Flexibility

C)

©

A

Overall Evaluation

A

©

0

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, Fig. 4. Conceptual block diagram of power system for artificial light source. (1) It must match the solar-ray supply circuit. (2) The light spectrum must be close to that of solar light. 5.7.3 Characteristics of Xe lamp: The only artificial light that satisfies these requirements is the xenon lamp, which, in the visible band, presents a smooth spectrum close to that of solar rays, though slightly biased toward blue. The xenon lamp also has the advantage of being susceptible of arrangement with spark gap small enough to ensure focusing into conductor rod. The characteristics of the Xe lamp are outlined below with respect to efficiency, power, aging and deterioration. (1) Spectrum: The spectrum of emitted rays presents prominent peaks in the infrared region, which requires to be eliminated. Heat'rays, also extremely strong, cannot be adequately removed by passage through quartz rod, and a heat reflecting glass must be inserted in the system. (2) Efficiency: The efficiency depends on such factors as Xe pressure, spark gap length, electrode length and current. As a general tendency, efficiency increases non-linearly in relation to the power. (3) Power Consumption: Since efficiency tends to increase with power, that is, the size of the lamp, the use of larger lamps will reduce overall power consumption for a given total output. (4) Aging and Deterioration After lighting a Xe arc lamp for 1000 h (about 90 days), the light flux will deteriorate to 60-80% of the initial value.

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and artificial, spectra were derived by averaging 3000 measurements lasting 0.1 sec each made over periods of 5 min (see Fig. 5). 2) At the same time, light delivered from the solar ray supply system was similarly analyzed with another optical multichannel analyzer, placed at a distance from source such that the area of projection equaled that of the solar-ray collector, with component intensities averaged over the range of beam angle. 3) From the spectra of direct solar rays and of the light delivered from solar ray supply system, the transmissivity curve of the solar-ray supply system was derived (see Figs. 6 and 7). 4) Applying the above transmissivity curve to the known spectrum of solar rays in space, the estimated spectrum was obtained for the light that would be delivered from a solar-ray supply system installed on a space station (see Fig. 8). 5) As auxiliary artificial light source during lack of solar ray incidence on space station, the xenon lamp was

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6. LIGHT DELIVERED FROM SOLAR RAY SUPPLY SYSTEM AND FROM ARTIFICIAL SOURCE

1) Direct solar rays and skylight were analyzed by optical multichannel analyzer at noon in Tokyo, in July 1984, for conditions of minimum air mass. To account for the constant fluctuations in light source, both natural

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Fig. 5. Spectra of solar rays reaching Earth surface and delivered from HIMAWARI. A: Direct solar rays on Earth surface (in Tokyo under overcast sky). B: Light delivered from HIMAWARI system of 60% transmissivity. C: Spectral luminous efficiency curve of normal man. D: Absorption curve of chlorella.

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6.1 The experiments were conducted in the following steps

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76

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Fig. 7. Spectra of solar rays in space and of light delivered from HIMAWARI system installed in space station. A: Observed solar spectrum in space. B: Estimated spectrum of light delivered from HIMAWARI system in space station. C: Spectral luminous efficiency curve of normal man. D: Absorption curve of chlorella.

Fig. 9. Arrangement for measuring rays from Xe lamp delivered through simulated solar-ray supply system. (1) Xenon lamp: power--3 kW; operating--25-30 V; operating--70-1 l0 A. (2) Power supply: a.c. voltage--200 V; a.c. current--14 A; a.c. power--4.9 KVA; phase--3; d.c. voltage--20-32 V; d.c. current--100 A. (3) Heat reflecting glass. (4) Polymer clad quartz rod 30 mm × 3 m. (5) Quartz lens f = 50 mm. (6) Acrylic filter. (7) Optical multichannel analyzer.

of man. Hence, the present system is ideal for such uses on space station as room lighting and sunbathing for the crew.

considered the most suitable. For this reason, measurements were made of the rays emitted by this lamp and delivered through the simulated solar ray supply system, shown in Fig. 9. The light from xenon lamp is passed through the heat reflecting glass (3) to remove the strong heat rays contained in the spectrum, then led into the polymer clad quartz rod (4). Upon emerging from the other end, and after passing through the quartz lens (5), the light is again filtered through arylic resin (6) to eliminate ultraviolet rays before entering the optical multichannel analyzer (7), which periodically sweeps across the circle of projected light (Figs. 10 and 11).

If the system is to be applied to experiments on plant and algae, their absorption curves being double-peaked with maxima in the violet/blue and red bands, the transmissivity characteristics of the solar-ray supply system need to be accomplished by either:

6.2 Concluding remarks

(a) collecting solar rays separately by units with light conductor inlet end positioned to best admit violet/blue and red rays, and then combining the two collected rays to constitute light with double-peaked spectrum; or (b) enlarging the light conductor inlet cross section to admit a broader spectrum of focused rays, which would then have the violet/blue and red bands raised in level. This method would permit the crew, as well as plants to enjoy the extended spectrum of rays delivered by the solar-ray supply system.

1) As it is clear from the transmissivity curve of Table 5 the transmissivity of the present solar-ray supply system is devised to match the spectral luminous efficiency curve

Further study will be required to determine for each application the optimum means of utilizing the elements presented in the above two cases.

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Fig. 10. Spectral composition of Xe lamp. A: Spectrum of controlled light from Xe lamp, without passing heat reflection glass. B: Ditto, after passing heat reflection glass. C: Spectral luminous efficiency curve of normal man. D: Absorption curve of chlorella.

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77

harmful components in the invisible bands completely eliminated. For the human body, sunbathing in light from solar ray supply system has been demonstrated in experiments on earth to be safe and beneficial (see Fig. 8)[1,6]. 3) The controlled output of a xenon lamp was found to closely resemble in spectral composition the visible spectrum of skylight on earth surface. The xenon lamp should thus serve usefully in a space station to substitute skylight on earth, in sustaining the basic biological activity of both men and plants. Substitution of solar-ray supply by xenon light during the periods of solar-ray shortage will generate a condition simulating cloudy sky on earth (see Fig. I 1). 4) Plants have proved to grow as strongly as under full natural sunlight when illuminated at 1/10 intensity with light delivered from solar ray supply system, Delivery of solar rays at 1/ 3 intensity of natural sunlight was found to further accelerate plant growth[4-6]. 7. SOLAR-RAY COLLECTOR SYSTEM

2) A solar ray supply system installed on space station will deliver light far more stably than on earth surface, and at about triple the intensity compared with direct solar rays in Tokyo, and comparable to the value under the equator. Moreover, the system will supply light with all the

7.1 Solar-ray collecting unit Solar-ray collection is performed by Fresnel lenses assembled in honeycomb lattice as illustrated in Fig. 12. Each unit is covered on the front face by a protector serving also as filter. The protector is of quartz, resistant to scratching, and sufficiently thick to withstand to some

Table 5. Comparison of intensity and quality of various kinds of light considered in study Luminance (Lux) I. Direct solar rays on earth surface (July 1984, Tokyo)

32,057

2. Direct solar rays delivered from HIMAWARI

21,409"

3. Observed solar constant in space

126,417

4. Estimated solar rays delivered from HIMAWARI in space station

84,487*

5. Scattered skylight 6. Xenon (a) Max. 100 A, 24 V Med. 60 A, 20 V Min. 7. Xenon (b) Min.

485* 320,000tet 166,500ttt 277tt 252tt

Total Flux Per Unit (0.0698 m2) (Lumen)

Chromaticity (K)

Remarks

2,237**

4,944

Observed (Figs. 5 and 8)

1,496

4,857

60% Transmissivity Tokyo, July 1984 (overcast) (Fig. 5)

8,824**

5,822

Observed (Fig. 7)

5,897

5,488

Estimated (Fig. 7)

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5,786

Observed (Fig. 1l)

23,540t 6,871t

6,020 6,008

Thermal reflection filter + Quartz rod + Quartz lenz (Figs. 9-1 l) Thermal reflection filter + Quartz rod + Quartz lenz + Acryl plate (Figs. 9, 11)

* Average illuminance of delivered light projected on a surface of area equal to that of solar-ray collector. ** Total flux of parallel light impinging on illuminated surface. t Total flux of utilizable light finally obtained from 3 kW Xe lamp (intensity too strong to permit determining spectral characteristics). t t Value determined upon attenuating the intensity to permit spectral characteristic measurement. t t t llluminance at center of illuminated circle 1 m diameter, at 1 m distance from quartz lens at terminal end of quartz rod.

K. MaRl et a/.

78

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Fig. 12. Solar-ray collecting unit. Composed of mini-lenses totalling 698.8 cm2 effective collecting area. extent impinging meteoroids, debris and deposits that may be encountered. Moreover, in the event of damage to the protector, the affected unit can be cut off and sealed off from the rest of the system, which will thus be able to continue functioning independent of the damaged unit. The space between protector and array of Fresnel lens is filled with inert gas, to permit temperature control and to suppress evaporation of the component materials (Table 6).

(Unit-mini

Fig. 13. Multiunit collecting panel. Alternative arrangements: 1 panel of 127 units = 8.87 ms. 2 panels of 61 units = 8.52 mL 4 panels of 37 units = 10.34 m2. Possible alternative arrangements are, as indicated under the drawing, 1-, 2- or 4-panel assemblies, with correspondingly smaller numbers of units per panel. For reducing the risk of functional impairment in the event of damage or failure, the 4-panel assembly might be considered advisable. The Fresnel lenses are of material resistant to radiation as well as to heat. They concentrate the solar rays by a factor of 10 000. The lenses are of single type, involving chromatic aberration. The entrance end of the light conductor is adjusted to

7.2 Multiunit collecting panel The solar-ray collecting units are, in turn, arrayed into multi-unit, collecting panels, as shown in Fig. 13. Table 6. The number of solar-ray supply units that can be substituted by 1 Xe lamp source

Collecting Unit I

k ~ w s s°lar-ray upply ystem Xe lamp N% Maximum Intensity 100 A, 24 V (23.5 Klm) Medium Intensity 60 A, 20 V (6.9 Klm)

In Space (5.9 Klm)

On Earth (1.5 Klm)

;°.r oo°. J ' 4 units

1.2 unit

15.7 units

4.6 units

Output of 3 kW Xe long compared with intensity of light delivered from solar-ray supply system in space and on Earth (value in table represent the number of solar-ray supply units that can be substituted by 1 Xe lamp source).

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Visible solar-ray supply system

79

feed the light into a single large diameter quartz conductor rod. This rod is connected to a rotative joint ensuring transmission of light through interface permitting rotative displacement between panel and supporting arm. Another rotative joint further transmits the light to the fixed stem of the gimbal. 7.4 Installation on space station An example of 4-panel collecting installation is shown in Fig. 15. The panels are so distributed as to minimize the number of panels that might lose solar ray incidence by shading or other reason. Fig. 15. Example of solar-ray collector installation on space station. REFERENCES

the focal point of green rays at midrange of the visible band, and of cross section such as to admit the entire visible band while letting more and more of the rays deviating in wavelength on both sides be diluted at the cable entrance on account of the chromatic aberration of the Fresnel lens. 7.3 Mounting the panel gimbal Collector panels are mounted on gimbals to permit angular attitude regulation following the movement of the sun's direction. As depicted in Fig. 14 showing the example of a 37-unit panel, the light conductors from individual Fresnel lenses are gathered together panel by panel, then the bundles of conductors from the panels are brought together at the pivot of gimbal where couplers

1. C. Wallis, Bring back the parasol; healthy looking bronze tan may lead to skin cancer, Time, p. 48 (May 30, 1983). 2. The Seventh International Study Tasks (IST) for The NASA Space Station Project, Study on Solar-Ray Supply System in Space Station (1984). 3. N. Tanatsugu, M. Yamashita and K. Mori, A conceptual design of a solar-ray supply system in the Space Station, Space Solar Power Review, 5, 225-230 (1985). 4. K. Mori, Microalgal cultivation for oxygen production using filtered sunlight transmitted through optical fibers, Proc. Second ISAS Space Utilization Symp., 109-112 (June 3, 1985). 5. K. Mori, Photoautotrophic bioreactor using visible solar-rays condenced by Fresnel lenses and transmitted through optical fibers, Seventh Symp. Biotechnology for Fuels and Chemicals, May 1985, Oak Ridge National Laboratory, Tennessee (to be published in Biotechnology and Bioengineering). 6. K. Mori, Value-added solar ray supply system, Expert, OHMUSHA, Ltd. 94-99 (Aug. 1983).